Local line voltage

[Dave A]

I had the Variac out today to run up my 21CT55 (not happy for another thread later) and the line side meter showed 130vac or so. I checked with my digi meter and a vintage Weston AC meter and got 129.6vac. Is that a bit high? I held the set to 115vac even though it was more like 120vac in the day. The local feed is 4k AC down to only 4 homes and a rural Telco CO.

[madlabs]

Yeah, that is on the high side. Sometimes it depends on where you live. In my rural area they put transformers along the long stretches to boost the sagging voltage. If you live near one of those your voltage will be hot. I live off the grid so no worries for me.

[Dave A]

150' from my xfmr. The Telco CO got a huge digital upgrade last summer and an new 3 phase xfrm set and a genny for outages. Big pull there.

[old_tv_nut]

I had similarly high line voltage at my home in Illinois. They checked and declined to do anything - I think they are mainly concerned with too-low voltage potentially damaging A/C units or other heavy motors. I haven't checked incoming voltage here in AZ in years, and don't recall what it was - just always use a variac on my CTC-5.

[madlabs]

Originally Posted by Dave A

150' from my xfmr. The Telco CO got a huge digital upgrade last summer and an new 3 phase xfrm set and a genny for outages. Big pull there.

The transformers I mean are HV to HV, not HV to LV like the one that feeds your house. Not that it makes mu difference, they probably won't do anything about it. I'd report it anyway just to see. A variac is a good option.

[Electronic M]

I tend to buy saturable reactor/ VRT, voltage regulating isolation transformers to deal with line voltage issues. They'll take anything from 90-140V in and depending on vintage of the transformer spit out a constant 110, 117 or 120V.
Local line voltage fluctuates enough to cause repeat noticable blooming by me, and I worry about it harming my rare early color sets so those regulating transformers are my solution.

[kf4rca]

Actually power companies use a capacitor bank to keep the voltage up at the end of long lines. They are usually rectangular looking devices.
https://electrical-engineering-porta...s-do-perfectly
( I had a summer job with an electric utility during college with SCE&G.)
Yes, what you need is a resonant regulated transformer. They have a third winding with a capacitor on it.
They also provide isolation.

[user181]

Just as an FYI, the parameter for line voltage requirement for power utilities is +/- 10% of nominal.

[kf4rca]

So you live on a 4KV circuit? Wow- that's old. That's what they started out with.
The new stuff is 13.8/23.9 KV. The 4KV transformers are usually dark gray and the 13.8 transformers are light gray. Also the new transformers are larger with larger insulators on them.
Most 4KV distribution is single phase and uses #6 hard drawn copper for the lines. The 13.8 stuff can be single or 3 phase. The insulators are larger and the lines are usually ACSR cable (Aluminum Covered Steel Re-inforced).
SCE&G still had some 4KV stuff out on the rural coastal island communities, so its still around.
Another device you might see on poles are OCR's. The oil circuit reclosers are automatic circuit breakers filled with oil. They are round with two insulators out the top.
Both capacitor banks and OCR's are used on 3 phase lines.
Did you know that up until 2007 Consolidated Edison in NYC offered DC to its wharehouse customers that still used DC elevators?

[Dave A]

The xfmrs show 4k on the side. The triple is the new feed to Verizon CO near my house. The single one is the local feed to four houses only. And the meter shows 134.9 at my house two nights ago. 126.6 today.

[old_coot88]

Originally Posted by kf4rca

Did you know that up until 2007 Consolidated Edison in NYC offered DC to its wharehouse customers that still used DC elevators?

Here in San Fran, there's a boatload of DC elevators dating back to 1906. The utility maintains a dedicated rectifier station just for them. The one in our building is a 1907 Otis, a working museum piece that still runs 24/7.

[old_tv_nut]

On a business flight once I met an elevator specialist who was flying on an emergency call for an elevator system. He told me that many buildings are unique, gear gets repaired but not replaced, and there is little uniformity even in the 21st century.

[Dave A]

Called PECO today to inform them of a shattered 4k pole behind me. No visit so far. And the local AC is now 146+. It goes up in the evening and around 126 during the day. Do I possibly have a home issue? Bad neutral connection, etc?

[Electronic M]

You can check for a floating neutral by finding 2 different phases (a 240V outlet for a stove, dryer, welder, AC unit, etc is a convenient place to measure) and checking neutral to ground on each phase. Both phases should have close to the same voltage.

Over 146V is nuts and shouldn't happen on a 120V circuit.

[kf4rca]

That looks like 13.8/23.9 stuff to me. And that's ACSR cable up there. Could be a loading problem with the other customers on that transformer.
I have never seen swings like that! Voltage does go up and down thru out the dayparts due to loading but shouldn't be that dramatic.
They'll probably send an engineer on something like that. They surely don't want any complaints to the public service commission!